Seeing that its pretty rare I turn my phone off, and the reboot after loading a rom are pretty painless and pretty rare again now that I'm set in what I have, I could personally do without the quick boot and/or hibernate.

Its a neat feature but I don't shut my phone off too much so I don't see it really being to important. Plus its just hibernation and not a true shut down. A battery pull still takes about 45 seconds after boot. I read an interview over at droid life and Chevy said he wanted to dig into the kernel more to work on screen sensitivity and things like that. I would rather see him use his time on that instead of this.

I think he is referring to putting the phone is standby/sleep mode with the screen off, not actually doing a full shutdown. With the data connection set to off, the phone is still active, you can receive text/pics, play music, have a bluetooth/wifi connection, etc without a data connection. All of those things I just mentioned will drain the battery to some degree. However, if you shutdown the phone completely, none of the stuff I mentioned before can take place resulting in a much longer battery life.

I think your thinking of sleep mode...
(Waiting for a touch of a key to wake it up)
This is hibernation. Everything is off. This feature
is best used when wanting to save battery and not have
the device on. At all.
Hibernation cannot be awoke by simple touch of a key.
It stores your last memory and resumes where you left off.